This invention relates generally to an apparatus of a type for thermal oxidation of silicon wafers, and for other processes of thermal treatment of silicon wafers and other semiconductors, and particularly to an improvement in a cap-mounting mechanism for the apparatus.
Prior apparatus of the type noted above are exemplified by Japanese (Laid-Open) Patent Publication No. 1977-154,360 of Tel-Thermco Engineering Co., Ltd., Japanese (Laid-Open) Patent Publication No. 1975-114,179 of Mitsubishi Denki Kabushiki Kaisha, U.S. Pat. No. 4,167,915 of Atomel Corporation, U.S. Pat. No. 4,154,192 of Mitsubishi Denki Kabushiki Kaisha, and U.S. Pat. No. 4,018,184 of Mitsubishi Denki Kabushiki Kaisha.
Other references of related interest include N. Tsuboushi H. Miyoshi, A. Nishimoto, and H. Abe, "Oxidation of Silicon in High-Pressure Steam", Japan J. Appl. Phys., Vol. 16, No. 5, pp. 855-856, 1977, and N. Tsubouchi, H. Miyoshi, A. Nishimoto, H. Abe, and R. Satoh, "High-Pressure Steam Apparatus for Oxidation of Silicon", Japan J. Appl. Phys., Vol. 16, No. 6, pp. 1055-1056, June 1977.
The apparatus of the patents and other references noted above are intended for thermal oxidation or other processes of thermal treatment of silicon wafers or other semiconductors at high pressures. Other forms of prior apparatus are intended for thermal treatment of silicon wafers or other semiconductors at low, ambient, or sub-ambient pressures.
Such apparatus are characterized by a tube, which is made of quartz, silicon carbide, or other refractory material of high purity and mechanical strength, and of chemical compatibility, and which is adapted to receive silicon wafers or other semiconductors to be treated, and a cap, which is made of the same material, and which is attachable to the tube, so as to enclose process gases within the tube, and which is detachable from the tube for insertion and removal of silicon wafers or other semiconductors through said end of the tube.
Conventionally, an open end of the cap fits onto an open end of the tube, near an outlet of the tube for process gases, so as to improve temperature distribution within the tube, and complementary sealing faces on the tube and the cap at their open ends enable a hermetic seal to be effected between the tube and the cap when the sealing faces are fitted to each other. Conical sealing faces are exemplified in Japanese (Laid-Open) Patent Publication No. 1977-154,360 of Tel-Thermco Engineering Co., Ltd., and in other references noted above.
Conventionally, the cap and a gripper, which grips the cap, are moved in mutually perpendicular directions (X and Y) at right angles to a longitudinal axis of the tube when the sealing faces are fitted to each other. However, if the cap has an uneven or irregular shape where the cap is gripped by the gripper, a longitudinal axis of the cap may be inclined slightly so as not to be parallel with the longitudinal axis of the tube, whereupon the sealing faces of the tube and the cap cannot be fitted to each other but interfere with each other. Thus, a hermetic seal cannot be effected between the tube and the cap, and the cap, the tube, or both can be broken.
This invention is addressed to a need for an improvement in the cap-mounting mechanism of an apparatus of the type noted above.